How does a SD starter survive drying / freezing?

We were discussing this question with a friend but our knowledge in microbiology is not so deep :(

The "wild" yeast and lactobacilli do not form spores, is that right?

So how come that the starter survives drying / freezing for longer storage?

Any idea what percentage of the SD microflora usually withstands the unfavorable conditions?

And is it better to dry / freeze the starter when it is at its maximum (just when I would use it or feed it) or rather when it gets more acid, when it falls back? Why? (the info I found on internet are not very consistent :(